Do we need four ways to diagnose a broken heart?

HibbsIn the 1960s, cardiac cath labs were created by adding a 35mm high-speed motion picture camera to an R/F room. Small catheters were developed to allow dye injections into the aorta, left ventricle and, finally, into the coronary arteries. The 35mm black-and-white film allowed cardiologists to diagnose regurgitant valves, bulging infracted heart walls and occlusions in coronary arteries. The cardiac cath procedure was the first, last and only study needed for the cardiologist to diagnose heart disease and refer a patient for open-heart surgery. But is this 40-year-old procedure obsolete in the face of so much new medical imaging technology?

At this year’s American Heart Association (AHA) meeting (Nov. 17-20 in Chicago) and again at the Radiological Society of North America (RSNA) conference (Dec. 1-6 in Chicago) the exhibits will be packed with high-tech computer-assisted methods to diagnose heart disease.

The ultrasound vendors will have outstanding demonstrations of color Doppler studies that demonstrate flow through the valves of the heart, through the aorta and most of the peripheral vascular network. The color-enhanced studies show forward flow in red and backward flow in blue. On the screen, electronic calipers can measure the long axis and short axis of the heart. They can calculate systolic and diastolic volumes with ellipsoid of revolution formulas and then subtract the systolic volume from the diastolic volume to calculate the stroke volume of the heart. By multiplying the heart rate and the stroke volume, they calculate the cardiac output. With the electronic calipers, they can measure the size of the heart valves and look at the flow gradient across those valves. There are even harmonic tissue characterization measurements that demonstrate muscle viability and contractibility. All of this high-tech analysis is done noninvasively. Using a hand-held probe, images can be obtained between the fourth and fifth ribs in most patients, under the rib cage in many patients and even using a transesophageal transducer (TEE probe) in some patients. The ultrasound technology to perform these great studies costs $200,000 to $300,000.

The nuclear medicine vendors will offer superior demonstrations of radioisotope-labeled cardiac marker injections that illustrate the mechanical function of the heart. They will show areas of perfusion and areas without perfusion. They can display relative volumes of blood flow. They can perform perfusion studies before, during and after exercise to determine changes in cardiac activity. They can perform calculations that demonstrate cardiac efficiency and response to stress testing or cardiac reserve. The nuclear medicine technology to perform these great studies costs $350,000 to $600,000.

The MRI vendors will showcase outstanding presentations of MRI angiography. There will be specific protocols of MRI imaging to emphasize blood flow, blood volume and turbulence. There will be protocols of cardiac function scoring based on extensive clinical trials. There will be new spectroscopy studies demonstrating soft-tissue occlusion formations. The MRI volume images provide a detailed 3-D model of the beating heart without any of the bone structure from the ribs or spine obscuring the image. The high-field-strength MRI technology to perform these great studies costs $1,500,000 to $2,500,000.

The PET scan or positron emission tomography vendors use a specific type of nuclear medicine procedure that highlights tissue metabolic activities. They propose that this is the only way to determine where there is viable cardiac muscle tissue that can be saved with coronary artery bypass surgery. They claim that bypassing occluded vessels to provide new blood flow to nonviable tissue is just adding additional surgical insult and injury to an already compromised heart. The cost of starting a PET scanning facility could cost $2 million to $4 million for the scanner and the cyclotron to produce the necessary isotopes.

But with all this great technology, which studies are required for a cardiologist to refer a patient for cardiovascular surgery? In the last 40 years — despite all these new, high-tech imaging, measurement and calculation packages — the basic cardiac cath is still the one and only study absolutely necessary for surgery. Despite the additional cost of all these newer and less-invasive procedures, recent interviews with 30 cardiologists revealed that all 30 would still perform the cardiac cath before sending patients to open-heart surgery.

Everyone uses the new technologies to “screen,” “rule out,” “quantify” or “document” the condition of the heart and the need for surgery. But physicians still want that electronically captured, “filmless” cardiac cath study to justify a surgical procedure.

Although some vendors, administrators and master planners consider the days of   the cath lab to be numbered, all the new specialty heart hospitals being built throughout the country have the modern $600,000 to $800,000 cath lab as their core component.

C. Wayne Hibbs is a 24×7 contributing editor with 30 years’ experience in clinical evaluation, technology assessment and equipment planning. His e-mail address is [email protected].